A navigation system uses a known technology of synthesizing a map image, which shows a current position and its surroundings, with a route to a destination, and displaying the synthetic image. A route line is superimposed on the map image with the color or thickness thereof changed, whereby the route is presented to a user. Otherwise, at an intersection or a branching point, an arrow indicating an advancing direction is displayed. These ideas have been proposed in the past. The arrow indicating the advancing direction is known to occupy part of a screen image so as to provide the contents described below.
(1) A distance from a current position to the next guide point to be presented and a direction in which a turn is made to reach the next guide point are displayed all the time (refer to FIG. 24A and FIG. 2 in Patent Document 1).
(2) When an intersection or any other guide point approaches, an enlarged view of the intersection is displayed in order to clarify a place where a turn is made (refer to FIG. 24B and FIG. 2 in Patent Document 1).
(3) A three-dimensional image showing an intersection or an entrance of an expressway in enlargement is displayed, and an advancing direction is indicated with an arrow (refer to FIG. 24C and FIG. 1 in Patent Document 2).
This navigation system may employ a large sideways elongated display whose diagonal has 6.5 inches or more. In this case, a portion of the screen of the display on which a current position mark is displayed and the other portion thereof on which information on a branch is displayed are, as shown in FIG. 24A, a bit separated from each other. A line of vision need be moved and the portions cannot be discerned at a time. When the portions are displayed as two screen images as shown in FIG. 24B and FIG. 24C, the current position is identified from the left-hand map image, and an advancing direction is recognized from the right-hand enlarged view. Anyhow, both the screen images must be checked.
For example, when a compact display whose diagonal has 6 inches or less or a display to be placed lengthwise is employed, there is difficulty in occupying part of the screen for the purpose of displaying a direction. When images are displayed as shown in FIG. 24B and FIG. 24C, the contents of display get complicated and the images become too small to see readily. Consequently, the technique of displaying two screen images cannot be adopted.                Patent Document 1: JP-H9-81895A        Patent Document 2:JP-H9-105642A        